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Organic certiﬁcation emerged as a grass- is available. For more information, see roots production and marketing tool during ATTRA’s Seed Production and Variety the 1970s and 1980s to ensure that foods Development for Organic Systems. labeled as organic met speciﬁed standards This publication focuses primarily on the of production. The Organic Foods Produc- certiﬁed organic growing of sweet corn, tion Act, a section of the 1990 Farm Bill, though some hard-to-ﬁ nd information of a enabled the USDA to develop a nationalRelated ATTRA more general nature is also included. For program of universal standards, certiﬁca-Publications basic production information including tion accreditation and food labeling. planting dates, regionally adapted varietiesOrganic Crop In April 2001, the USDA released the and local market outlets, contact the Coop-Production Overview Final Rule of the National Organic Pro- erative Extension Service in your area.Organic Farm gram. This set of national regulations stipu- In addition, marketing assistance is oftenCertiﬁcation and the lates, in considerable detail, exactly what a available through each state’s departmentNational Organic grower can and cannot do to produce and of agriculture.Program market a product as organic. Growers mustSeed Production and be certiﬁed, complete paperwork, pay fees Sweet corn varietiesVariety Development and undergo annual inspection. To learnfor Organic Systems Variety selection is an important consider- more about the details of the certiﬁcation ation in sweet corn production and includesOverview of Cover process, see ATTRA’s Organic Farm Certiﬁ- factors such as sweetness, days to maturity,Crops and Green cation and the National Organic Program.Manures seed color, size, yield potential and toler- The national law that took effect in Octo- ance to pests. The Cooperative ExtensionFoliar Fertilization ber 2002 essentially requires farmers sell- Service can provide a list of varieties rec-Farmscaping to ing produce labeled organic to be certiﬁed ommended for each region.Enhance Biological through a private or state-run certiﬁcation Cross-pollination of sweet corn with otherControl agency accredited by the USDA. kinds of corn or with some other sweetCucumber Beetles: corn genotypes can result in starchy-tast- Section 205.204 of the NOP states thatOrganic andBiorational IPM seed must be organically grown. Farmers ing kernels. Sweet corn will cross with may use untreated, non-organic seed when field corn, including genetically engi-Biointensive an equivalent organically produced variety neered varieties, but not with popcorns.Integrated Pest Generally, a minimal isolation distance of is not commercially available. Most certi-Management ﬁers require that certiﬁed organic sweet 250 feet between those varieties or typesNCAT’s Organic corn be produced from certiﬁed organic is recommended; 700 feet is preferred forCrops Workbook seed. Although breeding efforts are under- more complete isolation. Some authoritiesPostharvest way, varieties bred speciﬁcally for organic recommend a quarter mile, or 1,320 feet.Handling of Fruits production are not available at this time. Table 1 summarizes the general character-and Vegetables Only seed of the usual commercial varieties istics of sweet corn genotypes, includingDirect Marketing produced under organic management isolation requirements.Farmers’ Markets: Table 1: Sweet corn genotypesMarketing andBusiness Guide Genotype Sweetness Conversion of Isolate from Comments sugars to starchEntertainmentFarming and Normal sugary Moderately Rapid (sh2) varieties Early; germi-Agri-Tourism (su) sweet nates in cold soil Sugary Sweeter than Not as rapid as (sh2) varieties (se+) is sweeter enhanced (se), (su), less sweet (su) than (se) (se+) than (sh2) Super sweet or Very sweet Very slow (su), (se) & (se+) Longest shelf- shrunken (sh2) varieties life; germinates poorly in cold soilsPage 2 ATTRA Sweet Corn: Organic Production

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inches tall, additional nitrogen fertilizer will Seedling establishment not increase yield (Howell, 1998). • Plant seed 1.5 to 2 inches deep. Supplemental sidedress nitrogen fertiliz- • Plot rows no closer than 30 to ers used in organic vegetable production 36 inches. Rows planted closer include plant and animal by-products like together may cause nutrient stress, blood meal, ﬁshmeal and soybean meal, as be diﬃcult to cultivate and cause well as pelletized compost products. shaded conditions for overseeding in the fall. Table 2. Commercial organic nitrogen • Consider planting later than con- recommendations: Pounds of organic fertilizer ventional growers. With the use needed to provide variable levels of nitrogen (N) of untreated seed, organic sweet (Commercial Organic Nutrient Recommendations, corn growers often plant later, hop- http://anlab.umesci.maine.edu/handout/organ01.htm ) ing that warmer soil temperatures will encourage quick germination, 20 lbs 40 lbs 60 lbs 80 lbs 100 lbs Product Percent leading to better management of N per N per N per N per N per N annual weeds (Michalak, 2002). acre acre acre acre acre Pounds of product needed per acre: For suggestions on dealing with seed rots, see Cornell University’s Resource Guide for Organic 150 310 460 620 770 Blood 13% Insect and Disease Management. It is avail- meal able online at www.nysaes.cornell.edu/pp/ 330 670 1000 1330 1670 Cotton- 6% resourceguide. For information on ﬁnding this seed publication, see the Sweet corn integrated pest meal management portion of the Resources section at the end of this publication. 290 570 860 1140 1430 Soy- 7% bean meal 220 440 670 890 1100 Fish 9%Soil fertility mealNitrogen (N) is especially important in sweet 800 1600 2400 3200 4000 Alfalfa 2.4%corn production, not only for plant growth mealbut also for the production of amino acids This information, modiﬁed from an information sheet produced by the University of Maine, provides a handy guide to application rates forthat inﬂuence ﬂavor and nutrition. Research selected organic fertilizers to satisfy various levels of nitrogen needat Michigan State University showed that 6 (Commercial Organic Nutrient Recommendations).percent of the total nitrogen is taken upbetween germination and the sixth leaf stage,25 percent from seventh leaf to tassel, 25 Research in Connecticut determined thatpercent from tassel to silk and 39 percent 100 pounds of nitrogen per acre from com-during ear development (Evans, 1995). mercial fertilizer could produce optimum yields and economic returns for sweet cornA common recommendation in conventional (Bravo-Ureta et al., 1995). This research isproduction is to apply 50 pounds of nitro- signiﬁcant because it found the standardgen per acre prior to or at planting, followed rate used by Connecticut farmers, 160by side dressing with 60 to 80 pounds of pounds of nitrogen per acre, was too high.nitrogen per acre when the plants are 12 to In addition, it provides further support18 inches tall. for the organic farming practice of raisingThe Pre-Sidedress Soil Nitrate Test, also sweet corn in rotation with forage legumes.known as the Soil NO3-N Quick Test, can For example, it is generally accepted thatdetermine the need for any additional nitro- a healthy stand of hairy vetch can providegen fertilizer (Heckman et al., 1997). It around 100 to 125 pounds of nitrogen per acre to a subsequent crop.is now well established that if the nitrate-nitrogen level in the soil is above a thresh- Recent research on cover crops in Maineold level of 25 ppm when the corn is 6 to 12 substantiates this practice. In the Agronomywww.attra.ncat.org ATTRA Page 3

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Journal, authors of an article about cover illustrate the importance of photosynthate crops for sweet corn state: production in the early life of a corn plant, “Legume cover crops can supply all or most Schriefer emphasized the following facts of the N required by a subsequent crop if relating growth phases of corn to yield legume biomass is of sufﬁ cient quantity potential: and N mineralization is approximately syn- chronous with crop demand” (Grifﬁ n et al., • The number of rows of corn on 2000). the cob will be set ﬁve weeks after emergence. Rows usually range When legume stands are poor and therefore from 14 to 18. nitrogen is estimated to be lacking, supple- mental composts and organic fertilizers can • Ear length and number of dou- be applied as necessary. ble ears per plant will be estab- lished nine weeks after emergence For additional information on estimating (2000). nitrogen production and release from cover crops, see ATTRA’s Overview of Cover Crops Foliar feeding, like many eco-farming and Green Manures. methods, may be viewed as a sophisti-S cated organic agriculture practice. To weet corn Sweet corn does best with a pH of 6.0 to assist growers with technical details on does best 6.5 and needs moderate to high levels of crop manipulation through foliar feed- with a pH of phosphorus (P) and potassium (K). Rate ing, ATTRA has compiled the publication6.0 to 6.5 and needs of application should be determined by Foliar Fertilization.moderate to high soil testing. Rock phosphate, potassium sulfate (mined, untreated source), sulfate While corn is relatively drought tolerant,levels of phosphorus of potash-magnesia (commercially available irrigation increases yields, especially whenand potassium. K-Mag) and a limited number of other applied during silking and when ears are rock powders may be used in certified ﬁ lling. If irrigation is not an option and organic programs. weed management is good, plants might be seeded farther apart to reduce interplant One problem with rock phosphate is that competition. phosphorus is very slowly available. In cold soils, phosphorus deficiencies indicated by purple-tinged leaves may be apparent. Crop rotations, cover crops Thus, some growers drill a quickly avail- and weed control able source of phosphorus, such as bone An ideal rotation plan for organic sweet meal, at planting to insure readily avail- corn might look something like this: able phosphorus and a healthy crop stand. Other growers simply delay seeding until • Two years clover or legume pasture the weather and the soil warm up. • One year sweet corn Growers can apply and incorporate rock • Two years other vegetables mineral fertilizers, manures and bulk com- • One year small-grain nurse crop posts during ﬁeld preparation and bedding mixed with clover operations. Growers often make applications Corn typically follows pasture, hay or a in the fall before planting the cover crop. legume-based cover crop to take advantage Banding to the side of the row at planting of the nitrogen ﬁ xed by forage legumes. is another option, primarily in combination This is because carry-over weed problems with organic fertilizers or pelletized and for- are more easily managed with a row crop tiﬁed composts. like corn than with more narrowly spaced The late eco-farming adviser Don Schriefer vegetable crops. Many farmers see an advocated foliar feeding, used in combina- increase in corn yields of 5 to 7 percent tion with a chlorophyll meter, as a yield- following soybeans, and 10 to 15 percent enhancing corn production practice. To following hay (Michalak, 2002). Local organicPage 4 ATTRA Sweet Corn: Organic Production

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growers can provide advice on rotations and relay intercropping. ATTRA’s Overviewadapted to each region. of Cover Crops and Green Manures is recom- mended for a review of the beneﬁts and usesOne efﬁcient way to shift from vegetables to of cover crops and to gain access to impor-the small grain and clover mix is to plant tant cover crop resources such as Managinga spring or summer vegetable crop in the Cover Crops Proﬁtably, Sustainable Agricul-last year of the vegetable rotation. After ture Network Handbook No. 3 and the UC-the vegetables are harvested, the ﬁeld is SAREP Cover Crops Database.seeded down to a cereal grain and clovermix. This usually occurs in early to mid Weed control in organic sweet corn is basedautumn. When the cereal grain such as on a good rotation and timely mechanicalrye, wheat or oats is harvested the follow- cultivation. Two rotary hoeings followed bying spring, the clover is already well estab- two or three cultivations with sweeps andlished. Broadcasting cool-season cereal hillers are common means of non-chemi-grains and legumes into standing vegetable cal weed control. Flame weeding and livingcrops is another way to establish these win- mulches are complementary non-chemicalter cover crops. weed suppression techniques used in com- mercial production, usually as an adjunct toLong rotations like this are desirable mechanical tillage practices.because grass and legume sod crops aresoil builders, whereas row crops are soil Crow Miller, a Midwestern organic vegeta-depleters. In addition to improving soil tilth, ble grower, explained his weed control tech-complex rotations greatly enhance the non- nique like this:chemical approach to weed control. Accord- “We typically rotary hoe seven days and 14ing to Eliot Coleman, author of The New days after planting corn, before weeds haveOrganic Grower, a well-thought-out rotation emerged. We cultivate anywhere from 20 tois worth 75 percent of everything else that 34 days after planting, when corn is 6 to 12 inches tall. Second cultivation is 35 to 50might be done, including fertilization, till- days after planting, when corn is 18 to 20age and pest control (Davis, 2005). inches tall” (2001).On the other hand, short rotations and On larger farms, specialized weeding equip-annual vegetable cropping are the norm for ment may be an affordable option. State-of-growers in many parts of the country. This the-art cultivating implements include rollingis one of the reasons annual cover crops are cultivators, ﬁnger tine weeders, ﬁnger weed-used so prominently in organic farming. ers, basket weeders, spyders, torsion weedersA typical cover crop system for organic sweet and spring hoe weeders. Steel in the Field, acorn is fall establishment of a winter annual handbook from the Sustainable Agriculturelegume or cereal grain and legume mix. Network, provides illustrations, descriptionsPure stands of vetch or combinations of rye and practical examples of 37 specializedand hairy vetch or wheat and crimson clo- tools used to control weeds. It features pro-ver are common. The cereal grains provide ﬁles of farmers using reduced- or non-chem-a fast soil cover and a signiﬁcant amount of ical weed control strategies and contains aroot biomass. The legumes ﬁx nitrogen. list of equipment manufacturers and distrib- utors (Bowman, 1997). Updated informationThe cover crop is then plowed down a couple on equipment suppliers can usually be easilyweeks in advance of the next season’s crop, obtained through an Internet search. ATTRAusually in mid to late spring, thus providing can help with speciﬁc requests about ﬁndinga green manure. The cost of the cover crop appropriate equipment.seed and a legume inoculant may be viewedas an organic fertilizer cost. Research and ﬁeld experience inCover crop and tillage systems adapted to weed control and cover cropssweet corn crops include clean-till, low-till, A New York study showed improved produc-no-till, mulch-till, strip-till, living mulches tion in sweet corn ﬁelds intercropped withwww.attra.ncat.org ATTRA Page 5

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white clover as a living mulch (Grubinger crops (hairy vetch, crimson clover and ﬁeld and Minoti, 1990). White clover was mul- peas) mixed with oats as a nurse crop. tivated or rototilled with the middle tines Researchers winter-killed peas, leaving removed, leaving strips of live clover grow- inadequate mulch cover. Vetch was the eas- ing between the corn rows. This procedure iest cover crop to sow into, while crimson is called partial rototilling. To suppress clover was the only cover crop that reseeded excessive regrowth of the living mulch, itself. Yields were highest with hairy vetch, researchers partially rototilled white clover at 2.6-plus tons fresh weight per acre two weeks after corn emergence. Waiting (DeGregorio et al., 1991). until the fourth or sixth week after sweet Mechanical roller-crimpers and rolling corn emergence to perform partial rototill- stalk-choppers are gaining increased atten- ing was less effective. tion as effective kill methods. These are Several Massachusetts farmers used pro- heavy-duty drum rollers similar to a culti- pane ﬂ ame weeders to control weeds in packer with horizontal, welded, blunt-steel organic sweet corn. The farmers created strips. When pulled through the ﬁeld, these a stale seedbed by preparing the soil and drum rollers crush and crimp the coverM ow-down then letting it sit for a couple of weeks to crop and leave residue lying ﬂat on the soil encourage weeds to sprout. The objective of surface, discouraging regrowth. By having and roll- the roller-crimper placed on the front of the the stale seedbed strategy is to kill these down emerging weeds without further soil distur- tractor, a seeder can be pulled at the samemethods can knock bance to avoid bringing new weed seeds to time, allowing for only one pass throughdown cover crops the surface. After the weeds emerge, farm- the ﬁeld. This not only reduces soil com-and provide a no-till ers ﬂ amed and immediately planted the paction, but also reduces energy and labor ﬁeld. Flaming may be repeated prior to costs. Research in Alabama showed thatmulch in vegetable crop emergence (Hazzard, 1994). rolling down cereal grains like rye, wheatproduction. and black oats was most effective after ﬂow- The University of Illinois developed a fact ering, or anthesis, and prior to soft dough, sheet with economic thresholds for weeds in or grain formation (Ashford et al., 2000). corn and soybeans. The fact sheet contains a chart that shows percentage of corn yield Overseeding cover crops into standing sweet reduction in relation to number of weeds corn, a technique known as relay intercrop- such as pigweed, lambsquarters and John- ping, is one way to achieve cover crop estab- songrass per 100 feet of row (Pike). lishment, usually with a goal to increase nutrient cycling as a catch crop, suppress Growers commonly use herbicides in associa- weeds as a living mulch or to enhance crop- tion with no-till production to chemically kill ping system diversity. cover crops. A series of research reports and farm trials show that mow-down and roll-down Researchers in New Mexico broadcasted for- methods can knock down cover crops and pro- age brassicas, rape and turnips into sweet vide a no-till mulch in vegetable production. corn at last cultivation, known as early intersowing, and blister stage of the sweet Flail mowers are an ideal piece of mow- corn crop, known as late intersowing. Inter- down equipment, but small-scale farmers cropping did not depress sweet corn yields. also employ rotary mowers (brush hogs) Researchers harvested sweet corn ears and and even string weeders (weed eaters) to stover in early September and brassicas in chop down cover crops. Timing is impor- November (Guldan et al., 1998). tant. Hairy vetch should be mowed when the legume is already ﬂowering. Delay mow- Insect pest management ing of rye until ﬂowering, when the anthers A large number of insect pests can attack are shedding pollen. sweet corn. The American Phytopathological Researchers in Connecticut direct-seeded Society’s 1999 Handbook of Corn Insects is sweet corn into ﬂail-mowed legume cover the standard reference (Steffey et al., 1999).Page 6 ATTRA Sweet Corn: Organic Production

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Among the most widespread and damagingare corn earworm, European corn borer,corn rootworm and cutworm.Corn earwormThe corn earworm (Helicoverpa zea) is thelarval stage of a moth that lays eggs in thecorn silk. Corn earworm is also known astomato fruitworm, cotton bollworm and soy-bean podworm. In most of the country, thecorn earworm is the most destructive pestof sweet corn. Corn earworm is particularlydifﬁcult to control because it is protected bythe husk while feeding. Organic pest con- Corn earworm. Photo by R.L. Croissant, Bugwood.org.trol strategies focus on variety selection andplanting dates, cultural practices to incre-ase natural biological control such as para- some growing regions, such as south Texassitism and predation, and the use of micro- and Mexico.bial pesticides. Naturally occurring biological control agentsManagement options begin with resistant that prey on corn earworm eggs and larvaevarieties. Sweet corn varieties that mature include lady beetles, lacewings, syrphid ﬂyearly, possess long, tight husks extending larvae, big-eyed bug, parasitic wasps andbeyond the tips of the ears or contain natu- parasitic tachinid ﬂ ies (Straub and Emmett,rally occurring earworm-repelling chemi- 1992). Farmscaping by developing insectcals in the silks show the most resistance to refugia through establishment of ﬂoweringearworm attack (Davidson and Lyon, 1987 plants grown in strips and ﬁeld bordersand Williams and Williams, 1994). Table 3 may encourage these beneﬁcial insects tolists sweet corn varieties known to possess stay on the farm.some level of resistance to corn earworm. One farmscaping strategy entails the esta-Northern growers can reduce the time blishment of sweet alyssum (Lobularia mari-sweet corn ears are exposed to corn ear- tima), a short-lived ﬂowering annual, inworm by using a short-season variety and occasional pest habitat strips or ﬁeld bor-planting early in the season (Wiseman and ders (Grossman and Quarles, 1993). ThisIsenhour, 1994). Early seeding is more ﬂower is particularly attractive to parasiticeffective as a cultural practice in nor- wasps that prey on corn earworm, as wellthern states where the corn earworm moth as caterpillar pests of cabbage-family vege-is migratory. The moth overwinters in table crops. See ATTRA’s Farmscaping toTable 3. Sweet corn cultivars with some resistance to corn earworm(Wiseman and Isenhour, 1994; Pleasant, 1994 ) Stowell’s Evergreen Bodacious Hastings SWE Silver Queen Hastings GB Burpee HP Viking RB Hastings CGS Burpee PL Supersweet JRB Hastings MER Burpee HC Golden Bantam Hastings KK Burpee ST Jubilee Hastings IOC Burpee ST Texas Honey June Hastings CAL Burpee IXSwww.attra.ncat.org ATTRA Page 7

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Enhance Biological Control for details and recent research proving that a vegetable oil resources on this topic. and Bt mix provides outstanding control. Ruth Hazzard, an integrated pest manage- In addition to habitat manipulation through ment specialist with the University of Mas- farmscaping, inundative release of the tiny sachusetts, wrote several informative leaﬂets parasitic Trichogramma wasps can enhance that describe a biointensive approach to sweet biological control. Levels of control achieved corn pest control, with detailed notes on vege- with Trichogramma release varied from 20 table oil and Bt mixtures. Several of these are to 100 percent (Miles, 1995). Favorable listed in the Resources section below. environmental conditions are important. For instance, when Trichogramma wasps To facilitate the farm-scale adoption of this are released, the cards bearing parasite approach, UMass Extension developed and eggs should be covered with a small tent released a hand-held, gun-style applicator to protect them from rain and sun (Shirley, known as the Zea-Later. The Zea-Later II 1992). Commercial insectaries can provide and the spray mixture for corn earworm additional information about timing, release control, made up of emulsiﬁed soybean rates and the preferred Trichogramma spe- oil mixed with Bt, are available fromM cies for speciﬁc regions. Johnny’s Selected Seeds. See the Sweet ost larval corn integrated pest management portion feeding Bacillus thuringiensis or Bt (trade names of the Resources section for purchasing is done include Javelin, Dipel, Condor and Lepi- information. nox), is a well-known microbial pesticideunderneath the husk Two other microbial pest control strategies commonly used to control lepidopterouswhere foliar sprays pests. However, aerial sprays of Bt are usu- that show promise for corn earworm controldo not reach. ally only somewhat effective against corn include parasitic nematodes in the genera earworm. This is because Bt must be inge- Steinernema and Heterorhabditis and the sted to be effective and most larval feeding entomopathogenic fungus Beauveria bassi- is done underneath the husk where foliar ana. Trade names include Mycotrol, Natura- sprays do not reach. lis and BotaniGard. In 2007 the University of Maryland’s annual IPM Activities Report In contrast, direct application of Bt mixed stated that use of B. bassiana had become with vegetable oil to individual corn ears, commonplace in certiﬁed organic vegetable applied two to three days after silks extend production. The report, available at www. to their maximum length, or full brush, mdipm.umd.edu/reports/index.cfm, said: works exceptionally well as an organic approach to corn earworm control. Howe- There are speciﬁc formulations developed for the organic market that have carriers … ver, direct application means application acceptable to OMRI. Beauveria bassiana (Bb) by hand and this is time-consuming. Use of has been very effective for us in controlling a machinery oiling can to inject the mine- whiteﬂ ies and green peach aphid. We found ral oil increases the efﬁciency of this pro- it could suppress thrips if you started [appli- cedure. According to Mineral-Oil Treatment cations] early…. We have worked with brand name BontaniGard, which is one of the more of Sweet Corn for Earworm Control, a USDA popular formulations of Bb. In most cases, circular published in 1942, one worker is it is best to apply Beauveria bassiana using capable of treating one acre, or 12,000 a high-volume sprayer and penetrate the ears, in an eight-hour day using one of these plant canopy to make contact with the pest mineral oil injectors (Barber). ... Unfortunately, in our ﬁeld tests with grow- ers we found that the available formulations Although mineral oil treatment for corn of Bb tended to clog commercial low-volume earworm originated in the 1940s, on-farm sprayers and we could not get even spore research trials in the 1990s in both Okla- distribution [in greenhouse use] (Maryland Cooperative Extension, 2007). homa (Kuepper et al., 1991), and New England (Hazzard and Westgate, 2001), The Insect Parasitic Nematodes Web site, a veriﬁed the utility of this approach, with SARE-funded project hosted by The OhioPage 8 ATTRA Sweet Corn: Organic Production

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State University, is a good place to ﬁ nddetails on the biology and ecology of par-asitic nematodes, retail suppliers and factsheets on application and use. The Web siteis available at www.oardc.ohio-state.edu/nematodes. The University of Nebraska-Lin-coln hosts a similar site, Plant and InsectParasitic Nematodes, available at http://nematode.unl.edu.The efficacy of natural pesticide spraysand augmentative release of biocontrolagents like Trichogramma depends on tim-ing. Pheromone traps are a common tool formonitoring the presence of adult corn ear-worm moths, telling the grower when egg- European corn borer. Photo by Frank Peairs, Colorado State University, Bugwood.orglaying is likely to begin. They also providean estimate of corn earworm population and on other exposed plant tissues. Afterpressure. the larvae are half-grown, they bore into the stalk, the ear or the thicker parts of theScouting and sampling for corn earworm leaf stem. Once inside the plant, Europeaneggs is a complementary monitoring tech- corn borers are difﬁcult to control, so mostnique. Earworm eggs are laid singly, usually management efforts are directed toward theon the corn silks. Newly laid eggs are white, egg and early larval stages.but develop a reddish-brown ring after 24hours. Eggs that have been parasitized by It is interesting to note that the EuropeanTrichogramma turn completely black within corn borer is one pest problem directlythe eggshell. Scouting for eggs and monitor- affected by soil management and fertilization.ing egg maturation can help increase corn Researchers at The Ohio State Universityearworm pest control, as optimum timing collected soils from three sets of neighbor-for spraying can be determined within 12 ing farms that had a history of conventionalto 24 hours. (inorganic fertilizers, pesticide inputs andDespite the best intentions and the great- corn-soybean rotations) and organic (animalest of care, some corn earworm damage manures and forage-based, long-term rota-may occur. If so, growers can shuck worm- tions) management. Researchers placed theinfested ears and cut the damaged ends off soil samples in pots and amended each soilat the tip. Consumers probably won’t even type for nitrogen using ammonium nitrate,know the difference, since shucked and cut fresh dairy cow manure or no amendment.corn has become a ready-packaged grocery Researchers raised the potted corn plants initem in recent years. a greenhouse and released European corn borer adults twice a week.European corn borer The researchers observed preferential egg-The European corn borer (Ostrinia nubila- laying. European corn borer adults laid 18lis) overwinters as a fully-grown larva in the times as many eggs on potted plants withstems and ears of corn plants, usually just soils from conventionally managed farms asabove the ground surface. As the weather on potted plants with soils from organicallywarms in the spring, the larvae pupate and managed farms (Phelan et al., 1995). Thisemerge later as adult moths. These adults study conﬁ rms similar observations mademate and the females lay eggs on the under- in the late 1970s during research compar-side of the corn leaves. The smallest larval ing organic and conventional farms in thestages of the ﬁ rst generation feed on leaves western Corn Belt (Kuepper, 2001).www.attra.ncat.org ATTRA Page 9

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Pest management options for European corn Bt var. kurstaki, the microbial pesticide, borer include the use of resistant varieties, is an effective control for European corn cultural controls such as adjusting planting borer. However, in order to be effective, the dates to avoid infestations, sanitation includ- Bt must be ingested before the larva bores ing the destruction of overwintering sites into the plant. Monitoring techniques are such as cornstalks, and biocontrol agents commonly employed to enhance accuracy and microbial insecticides. Please note that and timing of Bt applications. Foliar sprays making the best use of these tools requires should be applied just before or after tassel ﬁeld monitoring. Monitoring for European emergence, but before silking and before corn borer also includes inspecting areas larvae bore into the ear or stalk. Biointen- adjacent to the ﬁeld in addition to scouting sive Insect Management in Sweet Corn, a fact of the ﬁeld itself. sheet by Ruth Hazzard and Pam Westgate Release of parasitic Trichogramma wasps of UMass Extension, provides guidelines for into sweet corn looks promising as a bio- Bt control of European corn borer and corn logical control method, but this technique is earworm (Hazzard and Westgate, 2001). highly dependent on favorable environmen- USDA researchers working in associa- tal conditions. For release, the wasp eggs tion with Iowa State University state that are attached to cards, each card bearing Beauveria bassiana, the entomopathogenic between 100,000 and 140,000 eggs. Cards fungus, applied in granular form during should be placed from three to ﬁve acres whorl-stage of corn development, can pro- apart and covered with a small tent to pro- vide season-long control of corn borer pop- tect them from rain and sun (Shirley, 1992). ulations (Leopold Center, 2001). However, Optimal timing for card placement is when recommendations for commercial use are tassels are in the whorl stage. After the not well developed. New research ﬁndings wasps emerge, they parasitize European are assisting in development of non-Bt corn corn borer eggs. Insectaries have additional refugia planted within a measurable dis- information about timing, release rates and tance to Bt corn stands to allow the survival the preferred Trichogramma species for a of susceptible moths to mate with resistant speciﬁc area. Research reports show para- moths (USDA ARS, 2004). sitism rates ranging from 60 to 97 percent Destruction of European corn borer over- using T. ostriniae, an Asian Trichogramma wintering sites, or all crop residues and wasp (Hoffmann et al., no date). Cost for plant refuse in which the borers may spend these releases are about $13 per acre for the winter, is another control option. Stalks 60,000 wasps. should be well shredded prior to plowing or disking for this method to be effective. Corn rootworm The corn rootworm (Diabrotica) is a bee- tle that feeds on corn leaves and clips corn silks, thus inhibiting pollination. The females lay eggs in late summer. These eggs hatch the following May or June. The larvae attack corn roots, reducing yield and causing stalks to blow over easily in high winds. There are three common species of corn root- worm: the Northern, Western and Southern rootworms. Under most circumstances, cropCorn rootworm. Photo by Scott Bauer, USDA Agricultural Research Service, rotation is one of the most effective meansBugwood.org of controlling the Northern and WesternPage 10 ATTRA Sweet Corn: Organic Production

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species. In the late 1980s there werereports in several upper Midwestern statesof Northern corn rootworm emergence incornﬁelds that followed soybeans in rota-tion. This was the result of extended dia-pause in which eggs spent two years in thesoil before hatching, rather than the usualone year. This delayed hatch defeated com-mon corn-soybean-corn rotations (Swoboda,1988). Geo-referenced grid samples forNorthern corn rootworm, taken from 1995to 2000 from two study sites in easternSouth Dakota, show increased incidence ofextended diapause in Northern corn root-worm (Ellsbury et al., 2002). Cutworm. Photo courtesy of Clemson University - USDA Cooperative ExtensionThe Western corn rootworm also devel- Slide Series, Bugwood.org.oped means to overcome this simple rota-tion scheme. A new strain of the species, Cultural measures are the traditional meanswhich some scientists are calling the East- of cutworm control. Fall plowing of sod,ern phenotype, thrives in soybean ﬁelds as early spring plowing with delayed plant-well as in the pest’s traditional host, corn. ing, control of adjacent vegetation and cropOne factor seems to be the presence of rotation are commonly recommended. Land kept clean-tilled during the late summer isearly-maturing corn varieties that the adult rarely infested.Western corn rootworm ﬁnds less attractivethan still-succulent soybean plants (Holm- Under conditions where infestations mayberg, 1996). As a result, longer rotations occur, monitoring is encouraged to deter-featuring greater crop diversity are becom- mine if additional control is advisable.ing necessary to control these pests. Among the organic options for cutworm control are parasitic nematodes and Bt. BtThe Southern corn rootworm, also known is more effective when mixed with bran andas the spotted cucumber beetle, is con- molasses and applied as a bait. Anothertrolled by late planting and by fall and option is placing baits of corn meal or branearly spring plowing. Populations of all meal around the plant. When consumed,three species are suppressed by predatory corn meal and bran meal swell inside theground beetles, tachinid ﬂ ies and beneﬁ- worm and kill it. Similarly, a molassescial nematodes. See the ATTRA publica- bait can be made from hardwood sawdust,tion Cucumber Beetles: Organic and Biora- bran, molasses and water. Once ingested,tional IPM for more information. the molasses hardens and renders the pest helpless. Organically acceptable sprays ofCutworm pyrethrum or rotenone can also be used ifCutworms cut seedling corn stems at or applied late in the evening. Because thesenear the soil surface. Cutworms feed at pesticides have short residual activity,night and spend the day hidden in the several applications may be necessary.soil. Normally considered a minor pest,cutworms can be a signiﬁcant problem in Insect pest monitoringsweet corn following sod, in no-till cul- Commercial pheromone traps and otherture and in ﬁelds adjacent to grassy areas. monitoring devices such as black lightsThere are several species of cutworms that strategically placed in sweet corn ﬁelds andmay become pests in corn, but the black border areas provide an excellent means tocutworm is perhaps the most common. determine the time of arrival and the levelwww.attra.ncat.org ATTRA Page 11

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of infestation for several major pests, most Sources of pheromone traps and inte- notably the corn earworm and European grated pest management monitoring sup- corn borer. This information can improve plies include Great Lakes IPM and BioQuip control and in many cases save on spray Entomology Products. See the Sweet corn applications. integrated pest management portion of the Resources section at the end of this publi- The Cooperative Extension Service devel- cation for ordering information. oped several excellent publications and resources to assist growers in learning how to trap, scout and interpret results appro- Diseases priately for their locale. Sweet Corn IPM: Insect Pest Management is a 30-minute Smut video available through the UMass Exten- Smut is a fungal disease contracted while sion. See the Sweet corn integrated pest the corn plant is a seedling. White or gray management portion of the Resources swellings on any part of the plant are indi- section for information on obtaining the cations of smut. Crop rotation and resistant video. The video demonstrates the use of varieties are the primary means of control-T pheromone traps, ﬁeld monitoring, pest ling this problem. Sulfur and copper fun- he Internet action thresholds and pesticide application gicides can also be used. Growers should revolution- remove and destroy infected plants. for sweet corn pests in the Northeast. ized the wayagricultural Also recommended is the Northeast Sweet Rustinformation is Corn Production and Integrated Pest Man- agement Manual, a regional integrated Rust is another fungal disease. Infecteddistributed and pest management publication produced by plants have orange-brown raised spots onobtained, and quite the leaves, which gradually enlarge and the University of Connecticut. Filled with turn black before dying. Use rust-toleranta few integrated handy tables, color photos and illustrations, cultivars.pest management it includes helpful sections on cultural prac-materials are tices, cover crops, sidedress nitrogen rec- ommendations, sweet corn pests, integrated Stewart’s bacterial wiltavailable online. pest management monitoring and action Stewart’s bacterial wilt is a disease caused thresholds. See the Sweet corn integrated by a bacterium that affects sweet corn, espe- pest management portion of the Resources cially early-maturing varieties. This disease section for ordering information. Also, see can reduce yields and stunt or kill entire the University of Connecticut Web site at plantings. Some plants are killed in the www.hort.uconn.edu/ipm for updated sweet seedling stage while others may not show corn integrated pest management topics for symptoms until tasseling or later. Leaves the Northeast. develop long whitish streaks and bacte- rial slime oozes from any cut plant part. For additional background on trapping, Infected plants should be destroyed and scouting and similar integrated pest man- populations of ﬂea beetles — the vector for agement methodologies, request ATTRA’s this disease — should be kept low. Some Biointensive Integrated Pest Management. hybrid varieties are resistant. The Internet revolutionized the way agricul- tural information is distributed and obtained, Maize Dwarf Mosaic and quite a few integrated pest management Mosaic is a viral disease that typically materials are available online. Many of the attacks late-planted corn. It is best con- Cooperative Extension Service fact sheets trolled by resistant varieties. If suscep- and integrated pest management newsletters tible varieties are planted, it is important are now available only in electronic format. to remove Johnsongrass, an alternate host, A selection of Internet resources is provided from adjacent areas and keep aphids, the at the end of this publication. vectoring agent, in check.Page 12 ATTRA Sweet Corn: Organic Production

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Harvest Don Schlimme, a professor at the Univer- sity of Maryland, recommends the follow-The following are general guidelines for ing strategy for refrigerated storage of sweetorganic sweet corn harvest. corn. He uses enhanced or super-sweet cul- • The same techniques as conven- tivars harvested at optimum maturity. After tional sweet corn are appropriate. husking and de-silking, cut the stem end • Sweet corn should be handled dif- close to the cob and remove insect damage ferently and more carefully than on the tip end. Put the ears in ice water animal feed, or dent corn. until the cob temperatures reach at least 40 degrees. This will take from 15 to 30 • Organic corn must be kept separate minutes. Add 1 teaspoon of common house- from conventional corn in order to hold bleach per gallon of cold water to kill maintain its value and identity. Any microbes. Add 1 teaspoon of white vinegar equipment used for both organic per gallon of water to lower the pH. Remove and conventional crop harvest must the ears from the water, drain for only a be thoroughly cleaned before har- minute or two to avoid letting the corn warm vesting an organic crop. up, and place in a gallon-size plastic bag. • Although mechanical sweet corn Then refrigerate the corn at 40 degrees; harvesters are available, most har- usually colder than the average home refrig- vest is still done by hand labor. erator. Sweet corn held in this way will last two weeks; holding the corn at 31 degrees • Trimming the flag leaves off the will increase holding time to three weeks ears at harvest reduces kernel dent- (Aylsworth, 1995). ing since the leaves draw moisture from the kernels. Several methods are available for precooling • For more information on organic sweet corn after harvest. Vacuum coolers regulations, see NCAT’s Organic are widely used by larger commercial opera- Crops Workbook. tions. Hydrocooling by spraying or immersing in water at 32 to 38 degrees is the next- best method and more easily accessible onPostharvest handling a moderate scale, though it takes longer.Since sweet corn is a highly perishablecrop, postharvest handling is important. Crated corn needs to be left for more thanProper treatment at harvest will help ensure one hour in a hydrocooler to cool the corngood quality. to 41 degrees. Many growers, especially at small and medium scales of produc-Rapid removal of ﬁeld heat via precool- tion, prefer mesh or burlap bags to cratesing will help delay deterioration. Precool because the same container used for ﬁeldthe corn to 32 degrees Fahrenheit within harvest can be easily dunked into the tankone hour after harvest and hold it steady for cooling. Once cooled, the bags are readyat the same temperature (USDA, 1986). At for shipping or short-term cold storage.optimum conditions of 32 degrees and 95percent relative humidity, sweet corn has a After hydrocooling, the corn should be icedstorage life of ﬁve to eight days. After two during transport and holding. If precool-to three days, the product declines in ﬂavor ing facilities are unavailable, top icing isand tenderness. Sugar levels decrease less absolutely necessary. The standard packrapidly at 32 degrees. At 86 degrees, 60 for sweet corn is 42- to 50-pound cartons, wire-bound crates or sacks. Standard packspercent of the sugars may convert to starch should be used because sweet corn tends toin a single day versus only a 6-percent loss heat when kept in a pile.at 32 degrees. Even at 50 degrees, sugar isconverted four times more quickly than at For growers selling to local markets, har-32 degrees (Aylsworth, 1995). vesting during the cool morning hours andwww.attra.ncat.org ATTRA Page 13

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selling as soon as possible are techniques that make hydrocooling unnecessary. You- Local markets: Fayetteville, Ark. pick marketing is another means of avoiding The Fayetteville (Ark.) Farmers’ Market did not postharvest handling. For additional infor- have certiﬁed organic sweet corn in 2008, but mation, see ATTRA’s Postharvest Handling vendors marketed premium-quality conven- of Fruits and Vegetables. tional sweet corn at prices ranging from 50 cents per ear to six ears for $5 toward the end of the marketing window in late August. That Marketing and economics was up from 20 to 40 cents per ear in 2007. In different parts of the United States The produce manager of Ozark Natural Food organic sweet corn may be raised for ship- Co-op in Fayetteville said organic produce ping, for processing or for sale through prices are up 3 percent across the board this alternative marketing channels such as farm year, but he has discretion in marking up indi- vidual items. Although the co-op’s policy is stands, farmers’ markets or community-sup- to buy local “when available,” just about all ported agriculture systems. the store’s sweet corn is shipped in. In 2008, Farmgate or wholesale prices for organic corn sold at retail for $1.19 per ear; in 2007 the sweet corn are difﬁcult to determine. Sample manager was able to oﬀer it few times at 99 cents per ear. The customary markup is 100 crop budgets and economic information dif- percent (Freeman, 2008). fer widely from region to region and year to year. See Appendix for a crop budget tem- plate. Sweet corn yields vary widely depend- ing upon the stand, growing conditions, A 2001 survey done by the Organic Farm- weather and marketing channels, according ing Research Foundation reported that 82 to the University of California-Davis. percent of organic sweet corn is grown for commercial processing such as canning and freezing. Standards for sweet corn The survey found farmgate prices for organic Weights and measures sweet corn range from $1 to $3.50 per Crate = 4 to 6 dozen ears (North Carolina Extension, Organic Sweet dozen ears. A Colorado grower complained Corn Production) that “cheap prices through local supermar- 50-pound waxed cardboard box = 4 dozen ears kets and a local economy in recession” made (California Standards, Corn picked for shipping) it “difﬁcult to obtain the organic price pre- Bushel = minimum of 35 pounds of ears in the husk with minimum mium.” The window of availability for fresh 8-inch ears with full kernel development (U.S. Bureau of Standards) market sweet corn is small compared with Bushel of sweet corn = From 35 to 40 pounds (University of that of vegetables produced over a longer Nebraska Weights and Measures, www.ianrpubs.unl.edu/epublic/ season or more amenable to storage, so it is pages/publicationD.jsp?publicationID=603) not surprising that fresh market conventional Sweet corn = From 6 to 8 pounds per dozen (University of Georgia, competes with fresh market organic. Of 68 http://caes.uga.edu) U.S. organic sweet corn producers surveyed, Per acre yields 16 percent direct marketed. The producers Organic reported weather ﬂuctuations as the No. 1 826 to 1,240 dozen ears, or 248 crates (North Carolina Extension, factor affecting returns to organic vegetable Organic Sweet Corn Production) (Davis, 1997) growers (Walz, 2004). 560 to 720 dozen ears, or 4.2 to 4.5 tons (OFRF 2001 survey) See the Resources section for a variety of (Walz, 2004) crop budgets for sweet corn. Conventional 1,400 to 2,000 dozen ears, or 350 to 500 48-count boxes per acre. An attractive feature of growing sweet corn, This is about 17,500 pounds to 25,000 pounds, or 8.75 tons to 12.5 tons especially for the small farmer, is its market- per acre (UC Davis ﬁgures for conventional sweet corn production) ability. Sweet corn sells quite well at farmers’ 1,000 dozen ears average (Oklahoma Extension ﬁgures for markets and other direct-to-consumer venues conventional sweet corn production) and a good-quality product sells out easily and rapidly in most communities.Page 14 ATTRA Sweet Corn: Organic Production

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Table 4: Net dollar returns per acre of sweet corn: Central California coast †(Klonsky et al., 1994)Wholesale price received per 48-ear box (unhusked)Yield $5 $6 $7 $8 $9 $10 $11 $12200 -$814 -$614 -$414 -$214 -$14 +$186 +$386 +$586250 -$699 -$449 -$199 +$51 +$301 +$551 +$801 +$1,051300 -$583 -$283 +$17 +$317 +$617 +$917 +$1,217 +$1,517350 -$468 -$118 +$232 +$582 +$932 +$1,282 +$1,632 +$1,982400 -$352 +$48 +$448 +$848 +$1,248 +$1,648 +$2,048 +$2,448† Adjusted for changes in harvest costs due to yield.ATTRA has a number of marketing pub- Table 4 was developed from budget informa-lications that can be of particular use to tion on California organic production in 1994sweet corn growers. These include Direct (Klonsky et al., 1994). It shows the inﬂuenceMarketing, Farmers’ Markets and Entertain- of yield and market price on net returns. Thement Farming and Agri-Tourism. range of yields and prices shown are realis- tic for that state. It should be noted that evenMarketability is no guarantee of proﬁtabil- with high yields and an optimal market,ity, however. While sweet corn sells read- per-acre proﬁtability is less than $2,500.ily, it does not have a reputation as a money Growers with limited acreage would be wisemaker among small producers, though to consider alternative crops that have highermany use it to attract customers. potential net returns per acre.Table 5: Net dollar returns per acre of sweet corn: Maryland †Retail price received per dozen earsYield $1.50 $2.50 $3.50250 doz -$854.40 -$604.40 -$479.40500 doz -$479.40 +$20.61 +$270.61750 doz -$104.40 +$645.61 +$1,010.61† The total variable and ﬁxed costs developed in this budget were $1229.40/acreA 1999 production budget for organic be noted that the Maryland produc-sweet corn in Maryland produced a simi- tion budget used to create Table 5 foundlar but more modest projection of proﬁtabil- total variable and ﬁ xed costs per acre ofity (Anon., 1999). The data is presented in $1,229.40. A 1996 budget for organicTable 5. sweet corn in nearby New Jersey foundOrganic production budgets for many total variable and ﬁ xed costs of $1,901.13specialty crops can vary widely. It should (Anon., 1996).www.attra.ncat.org ATTRA Page 15